1. Field of the Invention
This invention relates to an arc welding process of the type in which an electrode is placed in a space defined by the inner surfaces of a weld groove in a lengthwise direction thereof, with insulating material interposed between the electrode and the inner surfaces of said groove. More particularly, this invention is associated with a submerged arc welding of the type described.
2. Description of the Prior Art
In the past, in various industries, such as the ship-building industry, the development of production-size welding of relatively shorter members of a hull, for example, such as the web of a sidelongeron or the face plate of a cross-tie, has created a fresh approach to arc welding of the type in which an electrode is laid in a weld groove in a lengthwise direction thereof, because of its simplicity and high efficiency. It appears that this conventional process meets the demand of modern manufacturers or ship builders. However, attempts of such natures suffered from many shortcomings. Particularly, the former case involved problems which arise from the balance of an electric power load and the treatment of a cabtyre cable, because it requires the use of a large electric power source. Particularly, in the case of multi-layer welding of a plate over 30 mm in thickness, difficulties arise due to the instability of the back bead, poor peelability of the slag, and poor notch toughness of the deposited metal, which are all attributable to the poor penetration of the weld due to an improper direction of the welding arc produced. Due to the nature of arc welding, there is no way to approach the welding of a weld groove having a small groove angle. Furthermore, even in the case of a weld groove having a wider root gap, if an electrode is placed somewhat off-set to either side of the weld groove, there results poor penetration on the side of the groove from which the electrode is further spaced. The improper direction of the welding arc such as has been experienced in the past will be explained in more detail hereinbelow under the "Detailed Description of The Invention."
Accordingly, a need exists for an arc welding process whereby a welding arc can be directed to the desired portion within the weld groove, with resultant deep penetration, such that the electric power required for the welding can be reduced by a considerable degree, and wherein the weld is free from deficiencies such as unstable back bead formation, poor peelability of slag and poor notch toughness of the deposited metal.